The present invention generally relates to mapping catheters for sensing electrical activity of the heart at localized locations of the heart. The present invention is more particularly directed to such a catheter which is capable of both sensing electrical activity of the heart at localized locations of the heart for mapping and for defibrillating the heart.
Mapping catheters or leads are well known in the art. Such leads include, at their distal ends, a plurality of closely spaced, relatively small surface area, electrodes. These electrodes may be disposed axially along the lead at the lead distal end or disposed in spaced apart and aligned relation about the lead at its distal end. Each electrode is coupled to a respective different connecter, referred to in the art as a tail, at the proximal end of the lead.
In use, the distal end of the lead is inserted through the skin of the patient into a vein or artery and then advanced so its distal end is within the heart or within a vein or artery associated with the heart. The connectors are then connected to external amplifier and display or recording equipment.
The lead is then manipulated or maneuvered into various positions. At each position, adjacent electrodes are utilized as electrode bipolar pairs to sense electrical activity of the heart. Because the electrodes are closely spaced, the electrodes sense electrical activity of the heart at localized locations and the resulting ECGs are displayed or recorded. The foregoing procedure is known as mapping and is utilized during electrophysiology studies.
During such studies, electrical energy may be applied to the electrode pairs to pace the heart. As a result of such applied electrical energy, fibrillation, such as atrial fibrillation, may accidentally be induced in the heart. Such fibrillation must be terminated by cardioversion before the mapping procedure can resume.
In order to cardiovert such fibrillation, in the prior art, it has been necessary to remove the mapping catheter and heavily sedate the patient. Once the patient is sedated, an external defibrillator with external pads is used to transthoracically cardiovert the heart. As is well known in the art, such external defibrillation requires high intensity energy.
Unfortunately, the need to externally defibrillate a patient undergoing a mapping procedure has many disadvantages. First, because some time may pass before the patient is sedated enough to be ready for external defibrillation, it can be more difficult to successfully cardiovert the heart. This may require higher defibrillation energies with the concomitant risk of causing large area skin burns on the patient.
Second, after successful cardioversion, patients may require thirty to sixty minutes of rest before the mapping procedure can resume. In some cases, patients are even required to rest overnight in the hospital before the mapping procedure can resume the next day. This obviously increases the time and inconvenience in completing a mapping procedure. Another disadvantage is that it is often difficult to replicate the last position of the mapping catheter when the mapping procedure is resumed. This lends to decreasing the accuracy of the mapping procedure results.
The present invention overcomes the aforementioned disadvantages of the prior art. To that end, the present invention provides a temporary mapping catheter capable of both sensing electrical activity of the heart at localized locations of the heart and defibrillating the heart when defibrillation is required. In accordance with one embodiment of the present invention, the mapping catheter may further be used for applying electrical energy to the heart for establishing pacing or defibrillation thresholds.